1. Field of the Invention
The present invention relates to reader/writer antenna modules, and in particular relates to HF-band reader/writer antenna modules preferably for use in short-range communication with radio frequency identification (RFID) tags and to antenna devices including HF-band reader/writer antenna modules.
2. Description of the Related Art
An RFID system in which communication is performed between a reader/writer and an RFID tag using a non-contact method so as to transmit information between the reader/writer and the RFID tag is an example of a known merchandise management system. The reader/writer includes a wireless IC for processing wireless signals and an antenna for transmitting and receiving wireless signals. Predetermined information is transmitted and received in the form of high-frequency signals via an electromagnetic field between an antenna of the RFID tag and an antenna of the reader/writer.
In recent years, the field of use of RFID systems has been becoming wider and wider and there are applications in which a reader/writer is mounted in, for example, a mobile communication terminal. Consequently, reader/writers have been becoming increasingly smaller in size and card-type reader/writer antenna modules have been proposed such as the one described in International Publication No. WO 2007/105469. This antenna module has a structure in which an antenna conductor, a semiconductor memory and so forth are integrated with flexible wiring substrates, and a substrate on which an antenna conductor has been provided and a substrate on which a chip-type component such as a semiconductor memory has been provided are stacked one on top of the other and the substrates are connected to each other with flexible lead wiring.
In this structure, the substrate on which the antenna conductor is provided is stacked on a surface of the substrate, on which the chip-type component is provided, on the side opposite to the surface on which the chip-type component is provided. Consequently, the chip-type component is exposed on the surface and in order to protect the chip-type component from external noise and external stress, for example, a metal case or a resin layer needs to be separately provided. In addition, the substrate on which the antenna conductor is provided and the substrate on which the mounted component is provided are directly affixed to each other and therefore the curvature of the lead wiring connecting the substrates is small and sometimes the reliability of conduction between the substrates is not sufficiently secured due to the large bending stress acting on the lead wiring.